The Australian Diagnostic Criteria for Contrast-Induced Encephalopathy

Introduction: Contrast-induced encephalopathy (CIE) is a recognised complication of contrast administration, however diagnosis remains challenging due to its symptom overlap with other neurological conditions and the absence of formal diagnostic criteria. Methods: A modified Delphi study was performed. Consultant physicians with active clinical experience with CIE patients were invited from neurovascular centres in Australia. Initial diagnostic items were derived from an extensive literature review and analysis of local institutional cases across Australia. Three Delphi rounds were conducted. Consensus was defined as ≥ 75% agreement. Results: Seventeen neurovascular specialists from nine neurovascular centres participated (81.0% response rate) between May 2024 and July 2024. In round 1, 15 diagnostic items were presented to participants, which were revised and one additional criteria suggested. In round 2, 14/16 diagnostic items achieved consensus. In round three 14/14 items achieved consensus. Ultimately, a 14-item diagnostic criteria was developed based on participant consensus. The absolute criteria exclude CIE if symptom onset is more than 24 h after contrast administration, or if symptoms can be explained by vessel occlusion/territory ischaemia, intracranial haemorrhage, epilepsy, metabolic derangement, intracranial malignancy or head trauma. The supporting criteria indicate that CIE is more probable if symptoms are reversible, correspond with the distribution of contrast administration, or are associated with reversible contrast staining, cerebral oedema or cortical/subcortical MRI signal change. Conclusion: This study proposes a 14-item diagnostic criteria for CIE based on expert consensus in Australia. Further research is needed to refine CIE as a clinical entity.